Inbox from Google

The app has a lot of features to help make email more manageable. For example, it highlights important parts of emails — reservation times, ticket information, photos, shipping information, etc. — so you don't always have to open actual messages.

It also groups together similar messages, like promotions, which make them easier to delete, and allows you to create reminders on a to-do list.

And like Mailbox, Inbox also lets you snooze emails for later.

Available on: Android and iOS

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Outlook from Microsoft

iTunes

My colleagues love the Outlook iPhone app.

Outlook filters the most important emails to your "focused" tab. You can also quickly swipe to archive, delete, or "reschedule" (aka snooze) an email for later. You can also quickly arrange your inbox just by emails that have attachments.

Spark from Readdle

Spark is another great email app. Like many of the apps on this list, it filters the important messages and groups the ones that aren't so important. It also allows you to snooze emails for later and swipe to archive and delete messages.

You can also use Spark to notify you when you receive important emails.

Available on: iOS

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Gmail from Google

If you're one of the hundreds of millions of people who uses Gmail on the web, then you'll be familiar with Gmail's mobile app. The app separates your inboxes into "Primary," "Social," and "promotions," and you can use it with multiple accounts.

The search function, as you'd expect, also works very well.

It doesn't have all of the features of the other apps on this list, but its a classic and works well.